As a main structure of a liquid crystal display device, a display panel includes an array substrate and a color filter substrate arranged opposite to each other to form a cell, and liquid crystals arranged between the array substrate and the color filter substrate. During the cell formation, alignment films are applied onto inner surfaces of the array substrate and the color filter substrate, so as to enable liquid crystal molecules to be arranged in a certain direction through a corresponding alignment process. Then, the cell is formed through a vacuum cell-forming process.
Usually, a cell thickness of the display panel is controlled via a spacer arranged on the color filter substrate, and cell thickness uniformity is a very important index for the quality of the liquid crystal display device. In the case that an external force is applied to a surface of the display panel, the display panel may be deformed, and in the case of the sufficient large external force, the color filter substrate and the array substrate may be displaced relative to each other. Due to such displacement, a contact area between the spacer and the array substrate may change. At the moment when the external force is cancelled, it is difficult for the deformed spacer to return to its initial state due to the change of the contact area. Hence, at some regions where the spacers are displaced relative to the array substrate to a great extent, light may not be shielded by black matrices on the color filter substrate, and light leakage may occur, resulting in uneven brightness of the display panel. Such a phenomenon may be called as “mura”. The severity of the mura is in direct proportion to the relative displacement of the spacer. The larger the displacement, the region where the light leakage occurs, the larger the brightness at this region, and the higher the mura level.
Currently, the mura level is generally determined through human eyes. To be specific, display panel samples with mura may be selected through human eyes, and the corresponding mura levels may be determined. Then, a to-be-tested display panel may be tested by a tester, so as to subjectively determine the mura level of the to-be-tested display panel by comparing it with the samples. However, there are the following drawbacks. Because the mura level is tested by the tester's eyes, it is difficult to ensure the accuracy of a test result. In addition, due to the limitation of human eyes, it is impossible for the tester to record the mura at different regions accurately at any time, so the accuracy of the test result may also be adversely affected.